Sort dataframe by custom order

If you want to keep the column as character rather than factor, you can arrange based on a match to the order vector

rating_order <- c("AAA", "AA", "A", "BBB", "BB", "B")

df <-
  data.frame(
    Rating = c("A", "AA", "AAA", "B", "BB", "BBB"),
    Value1 = c(1, 2, 3, 4, 5, 6),
    Value2 = c(2, 3, 4, 5, 3, 2)
  )

library(dplyr, warn.conflicts = FALSE)

df %>%
  arrange(match(Rating, rating_order))
#>   Rating Value1 Value2
#> 1    AAA      3      4
#> 2     AA      2      3
#> 3      A      1      2
#> 4    BBB      6      2
#> 5     BB      5      3
#> 6      B      4      5

^{Created on 2022-01-20 by the reprex package (v2.0.1)}

Here is one approach using dplyr. In short, first sort by the letter grade, and then again by the number of letters. This would not work for ratings such as AAB, but from what I gather from your example this isn't the case.

library(dplyr)

data.frame(Rating=c('AAA','AA','A','B','BB','BBB'),
           Value1=c(1,2,3,4,5,6),
           Value2=c(2,3,4,5,3,2)) %>%
  mutate(grade = substr(Rating, 1,1), # Create a column with letter grade
         count = nchar(Rating)) %>%   # Create a column with number of letters
  arrange(grade, count) %>%           # Sort by grade, then count
  select(-grade, count)               # Optional, removes intermediary columns

#>   Rating Value1 Value2 count
#> 1      A      3      4     1
#> 2     AA      2      3     2
#> 3    AAA      1      2     3
#> 4      B      4      5     1
#> 5     BB      5      3     2
#> 6    BBB      6      2     3

^{Created on 2022-01-20 by the reprex package (v0.3.0)}

Sort dataframe by custom order

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